In vivo heat inactivation of serum can distinguish false positive cross matches in renal transplants

Renal transplants have traditionally been performed despite positive cross match if results are presumptively due to IgM antibodies. False positives have been distinguishable from true positives by dithiothreitol or dithioerythritol treatment to inactivate IgM antibodies. Heat inactivation, which renders the antibodies inactive, is an alternative to chemical amelioration.We retrospectively evaluated clinical outcomes of patients who had positive cross matches presumed to be falsely positive as determined by treatment with heat inactivation compared to controls with negative cross matches over a six-year period. A total of 414 transplanted patients had available cross match data: 355 with a negative cross match and 59 with a positive cross match rendered negative after heat inactivation. Serum creatinine was reviewed at 6, 12 and 24 months posttransplant.Graft function was considered stable at 12 and 24 months post-transplant if the change in creatinine compared to the 6-month value was >0.5 mg/dL. Repeated and nonrepeated measures analysis showed equivalence in the change in sCr from 6 to 12 (p = 0.525) and from 6 to 24 months (p = 0.752). Kaplan-Meier curves to evaluate graft survival demonstrated no significant difference in function over 24 months. Curves were censored for patient death, treated as death with functioning (p = 0.48) and nonfunctioning (p = 0.64) grafts.We have demonstrated comparable long-term function and survival for living donor renal transplants using heat inactivation to detect false positive cross matches. This simple and cost-effective method can be used to safely evaluate histocompatibility for living donor renal transplant recipients.